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http://commuteorlando.com/wordpress/wp-content/uploads/2017/09/logo_Commute_Orlando-webhead-650x214.png00Kerihttp://commuteorlando.com/wordpress/wp-content/uploads/2017/09/logo_Commute_Orlando-webhead-650x214.pngKeri2010-05-07 07:51:512010-05-07 07:51:51It's Not an Accident — Part 2

In my day job we deal with a large number of metrics and many of them are very precise, to less than 1 an a billion error in some cases. One of the things I try to impress upon folks, after learning it numerous times myself over and over, is to not take them at face value. Always look at them with a critical eye. Why? Because sometime the measurements will be incorrectly set up, sometimes there will be unaccounted for anomalies skewing the numbers and unfortunately far too often, incorrect conclusions will be drawn from the data.

Applying a critical eye to the above data I find I can’t draw much from it. It could be that all modes of travel are equally dangerous in which case the data above indicates that 45% of riding is done against traffic, another 25% is done on the sidewalk with traffic and that 6% of cycling is done by drunk riders. That could well be true, we’ve all seen that there are a lot of wrong way cyclists for example.

I posted in another thread that I didn’t know of any data indicating a safer riding mode. Since then I have become aware of a few studies which in the worst case indicate sidewalk cycling is 5x more dangerous than roadway cycling. I believe the raw data that created that graph shows around 50% of accidents involve the sidewalk, which if 5x more dangerous would mean roughly 10% of riding is done on the sidewalk. That could well be true also but in my very limited anecdotal sampling I believe I have witnessed a significantly higher proportion of sidewalk cycling than that.

As Jayeson notes, this chart (which came from my data at Metroplan) does not reflect risk, because we don’t know the exposure levels for those behaviors.

The point of the chart, as we use it in the CyclingSavvy course, is to show that only a small sliver of cyclist/motorist crashes involve sober, law-abiding roadway cyclists — about 8%. If you hear that 450 cyclists are hit by cars in the Orlando metro area each year, it sounds pretty bad. But if the story is “there were only 36 responsible roadway cyclists hit last year, and here’s how you can avoid even those few crashes” it changes the whole perspective of the cyclist.

Kevin and Peter are both WAY off in their interpretations of the chart. Many of the cyclist behaviors noted are legal, but they are riskier than legal roadway cycling. Riding against traffic on the sidewalk is legal, but it’s four times riskier than riding with the flow. Riding with the flow on the sidewalk puts you at higher risk for turning and crossing conflict crashes than riding with the flow on the roadway does.

This chart is not about “fault.” It is about understanding how few legally operating roadway cyclists are involved in crashes, and how those few remaining crashes can be avoided by the cyclist.
If one stops looking for whom to blame, one can start figuring out the actual scale of the problem and how to avoid it.

This chart is not about “fault.” It is about understanding how few legally operating roadway cyclists are involved in crashes, and how those few remaining crashes can be avoided by the cyclist.

If one stops looking for whom to blame, one can start figuring out the actual scale of the problem and how to avoid it.
Thanks for the explanation, Mighk.

I am convinced that within the cycling community there is far too much focus given to assigning fault and blame in safety discussion in general (e.g., oil spill), and bicycle traffic safety in particular. Fault and blame is only relevant after a crash to insurance companies, lawyers and judges. Robert Hurst has an entire chapter in his book, The Art of Urban Cycling, devoted to explaining this. For example, a crash involving the running of a red light is the fault of the red light runner, but such crashes can be avoided by checking for red light runners before entering an intersection, even on green.

In learning to be safer, we cyclists need to focus on what causes crashes, without regard to fault and blame, and what we cyclists can do to avoid those crashes. It’s a very different perspective, but a necessary one to assume in order to learn to be safer.

Show me a cyclist blaming a motorist for “causing” a crash or a close call, and I’ll show you a cyclist who is not learning to be safer.

IIRC, about half the crashes were legally the motorist’s fault. The good news for us is that motorist mistakes follow a pattern. They are predictable and we know how to discourage and avoid becoming victims of them. That’s the point of the chart.

Beginning at the upper right and moving our way around clockwise, we start by removing all the crashes that involved a cyclist going against the flow of traffic. Here in metro Orlando that is the most prominent crash factor. Some of those cyclists were on the sidewalk, some on the roadway. With the roadway crashes, the cyclist was automatically at fault. In some of the cases involving an against-the-flow sidewalk cyclist, the cyclist also violated some traffic law, such as red light running, or failure to stop at a stop sign. In the remainder the cyclist was not legally at fault, but the point here is that biking against the flow is much riskier.

Next we remove all the cyclist violations of the basic rules of the road that were left after the against-the-flow crashes were cut out. Some were on the sidewalk; some on the roadway. This includes biking at night without lights.

Then we remove all the remaining sidewalk crashes. These are ones in which the cyclist did not violate a law, and was going with the flow (so the motorists were at fault). The point here is that while it’s usually legal to bike on the sidewalk, doing so makes it more difficult for the cyclist defend against a motorist’s turning or crossing violation.

Then we remove intoxicated cyclists who were on the roadway and were not otherwise violating one of the rules of the road.

We are now left with crashes in which the motorist was legally at fault and the bicyclist was on the roadway, or where there was insufficient information on the report to make a determination.

The mid-block crashes (magenta) were mostly sideswipe-overtaking. Cyclists can prevent these by controlling their lane.

The intersection crashes (light blue) involve turning and crossing movements. Cyclists can prevent many of these by good lane positioning to ensure they are not in blind spots and can see conflicts earlier. Some of these of course are very hard to defend against. Some motorist-caused red-light-running and stop sign violations are simply beyond our ability to defend, just as they are when we drive automobiles. No bicycle facility can defend against them, either.

The remainder simply do not give us enough information, but some of these would likely be defendable by the cyclist.

Are there plans to show what the exposure rate is in the Orlando area? (or any area?) I’m seeing more and more cyclists and am curious to know. We’re still talking a small number of cyclists I would think in terms of crashes. Considering that people tend to want facts and science to dictate conclusions, there needs to be additional study to compare exposure to risk.

Oh, I know it’s damn near impossible to track, but that doesn’t mean it shouldn’t be figured out somehow. Surely there’s an engineer out there that would want to find a solution. Also, I’ll bet bikes can trip a counter and they are credited as an auto trip and not a bike trip.

I’m thinking video is probably more than likely a better solution anyway. Or RFIDs.

Keri, Mighk – great chart and data, thanks! Certainly helps show me how my behavior can help me avoid the vast majority of the situations where accidents occur.

OK, here’s a gruesome question … is there data to layer over these 7 segments to show the results of these incidents on bicyclists – police assistance (insurance and licence etc. checks) vs. hospitalization or other injury vs. fatality.

I’d be interested to see if there is data to show the seriousness of the consequence for the different types of behaviors … for example drunk cycling was a factor in 6% of accidents, but what if it resulted in 80% of fatalities? Or is it an even spread?

I didn’t do exactly the type of analysis you describe, but I did do a cross-tab of “approach types” (turning, crossing, overtaking, head-on) and injury severity, and with lighting conditions.

Night-time tends to involve a higher percentage of fatals and incapacitating injuries.

Many people assume that overtaking motorist crashes are more serious, and this is why they want to ride on sidewalks or some other type of separated facility. That is true when we include night-time crashes, but those almost always involve unlit cyclists. When we look at daytime-only it’s the turning and crossing conflict crashes that result in higher percentages of fatals and incapacitating injuries. Most overtaking crashes are sideswipes instead of full-on collisions.

About 12% of daytime crossing crashes are fatal or incapacitating; about 22% of turning conflicts, and about 8% of overtaking crashes (and none of those were fatals — none of the 17 fatals in our 2-year study period involved legally operating roadway cyclists).

Lane control helps to reduce both sideswipes AND the turning and crossing conflict crashes. And of course having front and rear lights will go a long way towards reducing night-time crashes.

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